Download Human Anatomy and Physiology

Human Anatomy and Physiology
CLS 224
Lama Alzamil
Email: [email protected]
3rd floor/ office # 117
The Muscular & The Skeletal System
(chapters 5 & 6)
The Skeletal System
1. Bones: An overview.
1. Bones: An overview
Objectives:
• Identify the subdivisions of the skeleton as axial or
appendicular.
• list the functions of the skeletal system.
• Name the four main classifications of bone.
• Identify the major anatomical areas of a long bone.
• Describe the process of bone formation, growth and
remodeling.
1. Bones: An overview
Function:
1.
Support.
2.
Protection.
3.
Movement.
4.
Storage.
5.
Blood cell formation (hematopoiesis).
Classification of Bones
206 bones in the human body
There are two basic types of osseous (bone tissue):
• Compact bone (cortical bone)is dense and looks smooth and
homogeneous.
• Spongy bone (trabecular bone)is composed of small needlelike pieces of
bone and
lots of open space.
The Skeleton is Subdivided into two
divisions
• Axial Skeleton:
Bones that form the
longitudinal axis of the body
(skull, vertebral column and
ribcage).
• Appendicular Skeleton:
Bones of the upper and
lower limbs, shoulders
and hips.
Classification of Bones on the Basis of
Shape
 Long bones
 Typically longer than they are wide.
 Cylindrical with knob-‐like ends.
 Are mostly Compact Bone.
 All the bones of the limbs, except the
patella (kneecap) and the wrist and
ankle bones, are long bones.
• Examples: Femur, humerus
 Short bones
 Generally cube-‐shaped
 Are mostly Spongy Bone
 Examples: Carpals, tarsals
 Flat bones
 Thin and flattened
 Usually curved
 Two thin layers of compact bone sandwiching a layer of
spongy Bone.
 Examples: Skull, ribs, sternum, pelvis.
 Irregular bones
 Do not fit into other bone classification categories
 Example: Vertebrae and hip.
Structure of Bones
Structure of a Long Bone (Gross)
Epiphysis:
 Ends of long bone.
 Composed mostly of Spongy Bone
covered by a thin layer of Compact
Bone.
 Covered by glassy hyaline cartilage
providing a smooth slippery surface
that decrease friction.
 The hollow spaces of epiphysial spongy
bone are filled with blood making
tissue called red bone marrow.
Diaphysis:
 The long shaft between the epiphysis.
 Most of the bon’s length.
 Composed of Compact Bone.
 It is hollow.
 Covered and protected by a fibrous
connective tissue membrane called
the Periosteum.
 Medullary cavity:
 The hollow center of the
diaphysis.
 Lined by a thin layer of
connective tissue called
Endosteum.
 In adults, it is filled with
adipose tissue called the
yellow bone marrow.
,While
 In infants, this area is filled
with red bone marrow.
Adult bone
Structure of a Long Bone
(microscopic)
Structure of a Long Bone
(microscopic)
-‐ Compact bone has a complex
structure filled with nerves, blood
vessels which provide bone cells with
nutrients and a route for waste
disposal.
-‐ Mature bone cells “osteocytes” are
found in cavities within the matrix
called lacunae.
• Lacunae are arranged in concentric
circles called lamellae around
central (haversian) canals. Each
complex consisting of central canal
and lamellae is called an osteon or
harvasian system.
• Central canals run lengthwise
through the bony matrix carrying
blood vessels and nerves to all
areas of the bone.
• Tiny canals “canaliculi”, radiate
outwards from the central canals to
all lacunae acting as a
transportation system connecting
neighboring bone cells to the main
nutrient supply.
• The communication pathway from
from the outside of the bone to
its interior (the central canals) is
completed by performating
(volkman’s) canals, which run into
the compact bone at right angles
to the shaft.
• This elaborate network of canals
causes the bones to be well
nourished despite the hardness of
the matrix.
• Calcium salts deposited in the
matrix give bone its hardness. The
organic parts especially collagen
fibers, provide the bone with
flexibility.
Formation of the Human Skeleton
• The Skeleton is formed from the most supportive tissues
in the body: cartilage and bone..
• In embryos, the skeleton is primarily made of hyaline
cartilage.
• During development, much of this cartilage is replaced by
bone.
• Cartilage remains in isolated areas:
– bridge of the nose
– Parts of ribs
– joints.
Bone Development, Ossification,
Osteogenesis
• For most bones, hyaline cartilage is used as the “model”
in the process of ossification.
• An exception is flat bones which use fibrous connective
tissue as a model for forming bones.
– osteoblasts (bone-‐forming cells), They can be stimulated to
proliferate and differentiate as osteocytes.
– Osteocytes (mature bone cells): Osteocytes manufacture
substances that make up the bone extracellular matrix.
Osteocytes are found enclosed in bone matrix.
– Osteoclasts (bone-‐resorbing cells): "clast" means to break;
osteoclasts break down bone.
Two Ossification types depending on the type of bone;
1- Intramembranous ossification :
- Occurs in Flat bones e.g.: ribs, pelvis and skull.
- Starts by mesenchymal stem cell within the embryonic
fibrous C.T. > develops into Osteoblast > Ossification centre
is initiated > organic portion of the bone matrix (Osteoid).
- Some Osteoblasts incorporates within osteoid to form
Osteocytes > osteoid becomes mineralized > forming spiky
needles (Spicule) that aggregates forming the supporting
structure or Trabecular.
- periosteum is formed and bone growth continues at the
surface of trabeculae.
2- Endochondral Ossification:
- hyaline cartilage is used as a model that get replaced by bone.
- Starts at embryonic stage.
-
8th week of fetus life, Chondroblast starts building hyaline cartilage
by forming Chondrocytes.
- the hyaline cartilage will then serve as a model, and will be
completely covered by osteoblasts.
- BV will infiltrate forming a ossification centre.
-
Ossification will extended at both ends to reach epiphysis.
- 12th week into development the epiphysis will be replaced by
spongy bone.
- Osteoclasts will start eating away the calcified tissue within the
centre, creating a hollow medullary space (cavity).
• Shortly after birth, most of its is replaced by bone.
• Some areas remain cartilaginous:
– Articular cartilage over the epiphysis, persist for life reducing
friction at the joint surface.
– The epiphyseal plate between the epiphysis and diaphysis.
– The epiphyseal plate provide for longitudinal growth of the
bone during childhood.
– This process of long bone growth is controlled during
childhood by the growth hormone and during puberty the
sex hormones. This ends during adolescence when the
epiphyseal plate are completely converted to bone.
Bone Remodelling
(cycles of resorption and formation)
Bones are remodeled continually in response to changes in two
factors:
(1) calcium levels in the blood
(2) the pull of gravity and muscles on the skeleton.
When blood calcium levels drop below homeostatic levels, the
parathyroid glands are stimulated to release parathyroid hormone
(PTH) into the blood. PTH activates osteoclasts, to break down bone
matrix and release calcium.
When blood calcium levels are too high (hypercalcemia) calcium is
deposited in bone matrix as hard calcium salts.
Terms
OSTEO = bone
Osteocytes =
Osteoblast =
Osteoclast =
Osteon =
Muscular system
1. Overview of muscle tissue.
2. Microscopic anatomy of the skeletal muscle.
3. Skeletal muscle activity.
1. Overview of muscle tissue
• The only body tissue able to contract. As a
result, muscles are responsible for all body
movement.
• “The machine of the body”.
• There are three basic types of muscle:
– Skeletal
– Cardiac
– Smooth
3 Types of Muscles
Classification of Muscle
Skeletal-‐ (muscle fiber)
Cardiac-‐ (x)
Found attach to the body’s Found in heart
Skeleton
Smooth-‐ (muscle fiber)
Striated, multi-‐ nucleated
Striated, 1nucleus
Found in viscera
(stomach, urinary
bladder, large
arteries..)
Not striated, 1 nucleus
Controlled by SoNS
Regulated by ANS
Controlled by ANS
Voluntary
Involuntary
Involuntary
Movement, maintain
posture, generate heat &
facial expressions
Heart beating
Peristalsis
Slow to fast
slow
Very slow
2.Microscopic anatomy of skeletal muscle
• Bundles of fibers that are bond together.
• Threads of myofibrils aggregate to form individual muscle
cell is called a muscle fiber.
• A muscle fiber is enclosed by a plasma membrane called
the sarcolemma.
• The cytoplasm of a muscle fiber is called a sarcoplasm.
• Nuclei pushed aside by the myofibrils that fill the
cytoplasm.
Muscle fibers form a larger bundle called fascicle, which
combine to form the largest robe (muscle).
C.T. within skeletal muscle
• Skeletal muscles are sheathed by a tough layer of connective
tissue called the epimysium. The epimysium joins muscle tissue
to tendons at each end, It also protects muscles from friction against
other muscles and bones.
• Within the epimysium are multiple bundles of fascicles, each of
which contains 10 to 100 or more muscle fibers collectively
protected by a perimysium. The perimysium is a pathway for
nerves & the flow of blood within the muscle.
• The thread like muscle fibers (the individual muscle cells), and each
cell is encased within its own endomysium of delicate connective
tissue.
• Myofibrils are chains of tiny contractile units called sarcomeres.
• Sarcomeres are the smallest functional units of a muscle.
•A sarcomere is
composed of two types
Of myofilaments :
• Myosin and Actin,
which are responsible
for muscle contraction.
• Myosin is a thick
myofilament, Actin is a
Thin myofilament.
• Each Sarcomere is
separated by Z-line at each
end.
• When muscles contract Zlines are pulled closer.
Another important muscle fiber
organelle
• The sarcoplasmic reticulum (SR), is smooth ER.
It releases calcium ions during contraction and absorbs them during
relaxation.
• Within the sarcoplasm, there are T-‐tubules that allow transport of
substances throughout the muscle fiber.
Troponin and Tropomyosin
• Troponin and
tropomyosin are
regulatory proteins
complexs involved in
muscle contraction.
Lies within the actin
filaments.
Neuromuscular junction
• Every skeletal muscle fiber is connected to a motor
neuron ending. This connection is called
neuromuscular junction.
• Between the end of the motor nerve and the muscle
fiber is a narrow space called synaptic cleft.
Skeletal muscle contraction steps:
• A skeletal muscle must be stimulated by a motor neuron to contract.
• When an impulse reaches the end of a motor neuron, it causes small
vesicles to release a neurotransmitter called acetylcholine (ACh) into
the synaptic cleft.
• ACh binds to receptors on the sarcolemma.
• The permeability of the sarcolemma changes allowing sodium ions to
enter the muscle cell generating an action potential (electrical
impulse) over the sarcolemma & flows inward along the T tubules.
• Calcium ions are released from SR. Calcium ions are the final trigger
for muscle fiber contraction.
•
•
•
•
The Ca2 binds to troponin on the actin filament, pulling away
tropomyosin exposing myosin binding sites. myosin heads
on the thick filament can now attach to the actin filament.
ATP provides the energy for the sliding filament mechanism.
Contraction occurs.
Muscle contraction ends when nerve impulses stop arriving at
the neuromuscular junction.
3. Skeletal muscle activity
https://www.youtube.com/watch?v=BMT4PtXRCVA